Drum Brake Questions

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bug1960
Posts: 23
Joined: August 3rd, 2007, 9:06 am

Drum Brake Questions

Post by bug1960 »

What size master cylinders are most people running ? Should they be different front to back ? I was having a heck of a time getting the car to stop at the end of a run last year. I am in the process of installing the residual pressure valves which I hope will help by holding some pressure for the initial stop. I need to be more comfortable with knowing the car will stop at the end of a run. Are most people running sotck pads or a different compound. This car is used strictly for Autocross.

Thanks for all the help and information. Im looking forward to the start of the season. (If I get the car back together)


Todd~
FM88
Lynn
Posts: 592
Joined: June 24th, 2006, 11:15 pm

Re: Drum Brake Questions

Post by Lynn »

I was using 5/8ths inch master cylinders for both circuits. I do have a balance bar, but I think it is set slightly to the front, but I'm not certain. The fronts lock first. Use stock brake shoes. Since these are not power brakes, it does take more leg power to get the car stopped, but with the right masters it isn't bad. I found the residual pressure valves helped with pedal travel and feel.
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FM4SOLO
Posts: 129
Joined: June 26th, 2006, 4:17 pm

Re: Drum Brake Questions

Post by FM4SOLO »

I just changed from 3/4 " MC's to 5/8", the improvement is significant. I use a balance bar, but have not had time to adjust it, left it as it was with the 3/4" setup. I just have to be careful not to lock up the brakes now 8)
Charles
bug1960
Posts: 23
Joined: August 3rd, 2007, 9:06 am

Re: Drum Brake Questions

Post by bug1960 »

So the smaller master cylinder has more braking force ??? Most people seem to go bigger ? Is it the interior of the cylinder that I need to measure to know what I am running now ?

Thanks
FM4SOLO
Posts: 129
Joined: June 26th, 2006, 4:17 pm

Re: Drum Brake Questions

Post by FM4SOLO »

Smaller bore Master Cylinders provide more line pressure for a given pedal pressure, but they require more pedal movement. I have to pay attention to brake shoe adjustment, as this plays a big part in pedal position. Most MC's are marked on the outside with their size (at least all of the ones I have are, old and new). It was a hard idea to wrap my puny brain around, but it worked. I bought cheap MC's and had to make some modifications to the brake line port (ground them down for less depth, and tapped them deeper) before I could get the lines to seal properly. It was a mess, and required many install, remove, modify cycles before I got it right. If I was to do it again, I would not have gone cheap, and would have saved many frustrating hours, lots of brake fluid, and several rolls of shop towels!

I love the world of F Mod, where you can and should work on your own car with simple tools. Now if I hadn't screwed up the 1/2 selector adjustment on my transaxle rebuild, I wouldn't be tearing it back apart. The good side is I now have working synchros, and a very nice set of 1.48 3rd and 1.04 4th gears.
Charles
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